The lentivirus human immunodeficiency virus (HIV) causes Acquired Immunodeficiency Syndrome (AIDS), a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. HIV/AIDS is a global pandemic, with most recent World Health Organization studies estimating nearly 34 million people are infected with HIV. This figure includes over 3 million children under the age of 15. Currently, no cure for HIV exists.
The HIV virus infects a large number of different cells in the body, including various cell types of the immune system, but its infection of CD4 T-lymphocytes largely underlies HIV pathogenesis. HIV-infection leads to reduced CD4 T-lymphocytes, further leading to progressive loss of cell-mediated immunity and an increased susceptibility to opportunistic infections.
The HIV virus consists of a viral envelope enclosing a capsid, which itself encloses the viral genome. The HIV envelope protein (Env) consists of precursor gp160 of the transmembrane domain gp41 (e.g., SEQ ID NO 1, which is one of many sequences for gp41) and the external domain gp120 (e.g. SEQ ID NO 2, which is one of many sequences for gp120), which are involved in virus-cell attachment. Mechanistically, gp120 attaches to the CD4 molecule present on T-lymphocytes, a series of conformational changes occur with gp120 and gp41, and gp41 mediates the fusion of the viral and cellular membranes and insertion of viral core and the genomic material into the target cell, resulting in host cell infection.
Conventional neutralizing antibodies generally consist of two identical heavy chains and two identical light chains, each with a single variable domain (VH or VL) at the N-termini of the molecule. More recently, neutralizing antibodies have been adapted to include a second variable region connected via a linker (L) sequence at the N-termini of the variable domains of a conventional molecule and are generally referred to as a dual variable domain immunoglobulins (DVD-Igs). DVD-Igs are immunoglobulin-derived molecules that contain two unique variable domains (V domains) linked to a constant region with the capability of tetravalent, bispecific binding, while retaining affinity and specificity of each of the parental antibodies. For example, DVD-Igs have been constructed that can bind both IL1a and IL1b, or IL-12 and IL-18. DVD-Igs have been proven effective in vitro and in vivo, and retain pharmacokinetic properties of the parental antibodies.
The idea of targeting two separate antigenic sites with a single antibody has also been directed against HIV. The most common approach has been to construct dual domain antibodies using an anti-gp120 V-region fused to CD4. When the inter-domain linker length was optimized, enhanced neutralization by these CD4-anti-gp120 immunoadhesins was obtained. Bi-specific antibodies with one V-domain against gp41 and one against gp120 have been produced; however the antibodies do not neutralize the virus as well as embodiments of the present invention. The failure to make effective neutralizing antibodies is due in part to the enormous sequence diversity of HIV-1, and the relative inaccessibility of conserved domains of the HIV virus.
Accordingly, there is need for novel antibodies and antibody like molecules and methods of neutralizing and eradicating HIV.